Equip the Striker shotgun. Aim the shotgun and quickly go into your inventory before the laser sight of the Striker has a chance to show up on screen. Equip any other weapon and exit out of your inventory. If done correctly, Leon will now run twice as fast, climb ladders twice as fast, knife twice as fast, and shoot twice as fast. The glitch will be canceled after a cutscene, an area transition, taking damage, opening doors, doing a quick-time event, or dodging an explosion.